Field of the Invention
The present invention relates to an ultrasonic type flowmeter apparatus and a method of using the same. Particularly, the present invention relates to an ultrasonic type flowmeter apparatus preferably used in a cardiac surgery for measuring a flow rate of a blood flowing through an auxiliary heart, in which a part of the ultrasonic type flowmeter apparatus is disposed in order to avoid undesired infection.
Related Art Statements
The ultrasonic type flowmeter apparatus comprises a conduit having, for instance a crank shape, and a pair of piezo-electric transducer elements each serving as an ultrasonic signal transmission and reception element are provided at both ends of a straight portion of the conduit. To this end, the conduit must include fitting portions, and furthermore the conduit has to comprise an inlet portion and an outlet portion. It is difficult to make the conduit by a single molding of synthetic resin. Therefore, usually a plurality of parts of the conduit are formed separately, and then these parts are assembled or composed by fusing or cementing to form the final conduit.
According to the above assembling operation, beads and debris might be produced within the straight portion of the conduit through which an ultrasonic beam propagates during the measurement. Moreover, centerlines of the fused parts might not be coincided with each other, and therefore a liquid could not flow through the conduit smoothly and an undesired turbulence might be generated. Furthermore, a length and an inner diameter of the straight portion might include error and a precision of securing the ultrasonic signal transmission and reception elements might be lowered. Therefore, flow characteristics of respective conduits are sometimes different from one another. In order to compensate the differences in the flow characteristics of respective crank-shaped conduits or inner reflection type conduits, it has been known to derive calibration data from measured values obtained in electrical measuring circuits by flowing a standard liquid such as water at known rates through the respective conduits. Then, the thus obtained calibration data is stored in memories installed in respective electrical measuring circuits. A pair of a conduit and a measuring circuit having a memory storing calibration data obtained for the relevant conduit is shipped from a factory.